The present invention is directed to a light bulb retention assembly, and more specifically to a retention assembly for holding a light bulb in an automobile headlight.
A light bulb, such as a light capsule for an automobile headlight, is typically inserted axially (without rotation) into a socket from the rear, the front of the headlight and socket being shielded by a protective lens cover. A seal may be attached to the periphery of a rear part of the socket. The socket has axially aligned and radially inward projections that mate with slots in the base of the bulb to prevent rotation of the bulb. The inserted bulb is held axially with a lock ring that is rotated into a holding position on the rear of the socket. The lock ring is held in position by rotationally mating retention surfaces on the lock ring with respective retention crevices on the socket.
The retention crevices for holding the lock ring can be formed in various ways, each of which presents problems during the manufacture of the assembly. For example, the mold for the socket (that may be part of a headlight reflector mold) may include slides or lifters formed by secondary molding actions. Since headlight reflectors are molded from high temperature polyester material, the molding process is not conducive to secondary molding actions because of the high molding temperatures and material flash problems. Further, molds that incorporate secondary molding actions are more expensive to build and maintain.
Another way to form the retention crevices for holding the lock ring has been to mill grooves or slots into the sockets. However, this creates a substantial dust problem that can degrade optical performance, even if steps are taken to reduce the dust. Further, the dust can cause health problems if inhaled and special care must be taken to ensure environmental quality.
A solution to the problems with secondary molding actions and milling has been to attach plates to the socket to create the retention crevices. However, the plates increase cost, must be attached with specific fasteners that mate with the plates, and require space that must be made available.
A further solution has been to use screws to define the retention crevices. The screws are spaced from the surface of the socket and the lock ring has a latching surface that fits beneath heads of the screws. The screws may also be used to hold the seal on the periphery of the socket. This arrangement is illustrated in FIG. 1 that is a rear view of prior art light bulb retention assembly. A light capsule 10 for an automobile headlight is inserted axially into a socket 12 and a seal 14 is attached to a periphery of a rear of the socket. Capsule 10 is held axially with a lock ring 16 that is rotated into a holding position on the rear of the socket. Lock ring inward projections 17 hold an edge of capsule 10. Lock ring 16 is held in position by rotationally mating latching surfaces 18 on the lock ring with respective retention crevices formed beneath screws 20 inserted into the socket. Screws 20 overlap an interior edge of seal 14. However, manufacture of this assembly requires tightening of the screws after placement of the seal. Further, the screws grip only small parts of the seal and can damage these small parts of the seal if too much pressure is applied by overtightening the screws.